1. Field of the Invention
The present invention is related to roof bolting assemblies designed to strengthen the roofs of mines and, more particularly, is directed toward a single-component, unitary roof bolt assembly which offers ease of storage, handling, and operation heretofore unrealizable.
2. Description of the Prior Art
Several designs of anchor bolts have been utilized for strengthening roofs in subterranian structures, such as coal mines, subway tunnels, and the like.
One of the more popular and widely accepted designs utilizes a standard rod or bolt which is secured within a drill or bore hole by means of an adhesive or grouting material. The advent of quick-setting adhesive resins has in fact popularized a two-component roof bolt assembly which consists of a destructible cartridge or capsule that contains the quick-setting resin and a hardening agent. The cartridge or capsule is first inserted into a drilled bore hole, whereafter the bolt is inserted, the cartridge is ruptured, and the bolt is held in place until the adhesive sets.
The foregoing technique is exemplified in U.S. Pat. Nos. 3,877,235; 3,703,790; 3,298,144; 3,302,410; and 2,092,341.
Each of the structures described in the cited patents unfortunately suffers from several disadvantages and inconveniences. In particular, the roof bolting assemblies described therein are comprised of at least two, and sometimes three, dis-united components in the form of the adhesive-containing cartridge or capsule, the roof bolt which is eventually adhesively bonded within the bore hole, and a means for rupturing the capsule or cartridge to release the quick-setting resin about the roof bolt.
Such multiple component assemblies require the installer of the roof bolt to match on-site a particular sized bolt with the separately provided capsule or cartridge in order to provide the most efficient combination for the particular bore hole being reinforced. Further, the separate components require more time and attention for installation than might be necessary if they were unitary, a multi-component assembly sometimes requiring two people for proper installation and setting. Additionally, the individual capsules or resin-containing cartridges must be separately stored from their respective roof bolts, which requires excess storage space and multiple inventory problems than might otherwise be necessary. Finally, the cost of installation in terms of labor necessarily should be minimized, a difficult objective when the installer is required to store, select and manipulate a two or three component roof bolt assembly.